Adaptive Skins and Microclimates

Plea2004 - The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19 - 22 September 2004 Page 1 of 1 Adaptive Skins and Microclimates Simos Yannas Environment & Energy Studies Programme Architectural Association Graduate School 34-36 Bedford Square, London WC1B 3ES, UK [email protected] ABSTRACT: The paper reports on a project that served as a key learning tool for this year’s post- graduate teaching programme. Starting with fieldwork and design proposals for sites in London, student teams proceeded with the design and construction of a small structure that was erected in April 2004 on the island of Santorini in Greece. Conference Topic: education and technology transfer; comfort and well-being in urban spaces Keywords: urban microclimates, outdoor comfort, adaptive skins, environmental software 1. INTRODUCTION experienced by sitting, standing or moving around the spaces affected. But they also affect temperature, soil The Architectural Association Graduate School’s moisture, and plant growth, and these in turn Environment & Energy Studies Programme (AA EE) contribute to the differentiation and characterization of explores the application of sustainable environmental the microclimate. The longer the exposure of an area design at the level of the city and the individual the more marked may be the resulting microclimatic building. An ongoing topic of investigation is the differentiation from an area not similarly exposed. relationship between built form and environmental How can we compile a microclimatic profile of an performance. A number of recent projects have area or site without having to embark on long-term focused on aspects of mixed-use development as measurements ? How much influence can we exert part of a zero carbon emission strategy for urban on the environmental variables characterizing a environments. Field studies undertaken in the context microclimate ? What means can we use to of these projects and reported in other papers, accomplish such modifications ? What are relevant [1][2][3][4], have revealed that the microclimatic applications? Sunshine duration and intensity, wind attributes of the urban tissue vary widely within any direction and velocity and the other environmental given segment of a city. As a result the urban tissue parameters all vary over time, both within the daily accommodates distinct microclimatic niches of cycle and seasonally, but also from year to year. unknown and unpredictable variability. Such What adaptive mechanisms can we employ to variability may be the outcome of built density and respond to this dynamic ? how can these urban geometry. Both these factors affect solar microclimatic tools become self-updating in their exposure and air flow within the fabric of the city, and environmental behaviour ? either of these climatic parameters can have a strong These questions provided the starting point for a effect on the microclimate of a site. Microclimatic learning process that combined theoretical, empirical variability can be also the result of anthropogenic and analytic studies as inputs to design proposals sources inside, as well as outside, buildings. A that were meant to be informed by environmental resulting problem for urban design, affecting both considerations from the outset. The lessons learnt building design and that of open spaces, is that and the design proposals developed in the course of generalised models are of limited use in helping to this process are briefly discussed in the following characterise and assess local conditions so as to sections of the paper. inform design. On the other hand, a promising inference is that a process of ecological regeneration 2. ADAPTIVE SKINS & MICROCLIMATES could be initiated by local interventions aimed at creating pockets of improved microclimate which can 2.1 Context contribute to reversing the negative effects of urban The Adaptive Skins & Microclimates project was climate change. This is a corollary of the observation introduced in October 2003 as a vehicle for applying that distinct microclimates can coexist in close the theoretical concepts and analytic tools presented proximity within the urban environment without one by the taught courses of the AA EE Masters negating the other. Programme. The first stage of the project involved The most significant microclimatic variations are observations and measurements indoors and in open commonly created by differences in sun and wind spaces around Central London. The objective at this patterns. Such differences have an immediate effect stage was to investigate the mechanisms underlying on the sensation of thermal comfort or discomfort different microclimates in the urban environment. The Plea2004 - The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19 - 22 September 2004 Page 2 of 6 variability and cloudiness of London weather and the strong effect that wind patterns have on outdoor thermal comfort were early observations by the eighteen Masters students taking part in the project. These observations led to design briefs that ranged from explorations of adaptive clothing to proposals for urban pavilions and the creation of dynamic landscapes for pedestrians in the city. Short-term readings of environmental parameters were undertaken in selected locations around London as part of diagnostic investigations and outdoor thermal comfort studies. Computer software that was introduced by the taught course for use on this project included: Meteonorm v5.0 for generating weather data [5]; Ecotect v5.2 software for 3-D studies of solar access, shading and daylighting and for analysis of weather data [6]; TAS for dynamic thermal simulation [7]; CFX-5 for air flow simulation [8]; and ENVI-met for outdoor microclimate simulation [9]. 2.2 Adaptive Topographies Following study of long-term weather data for Central London and short-term observations of sunshine, temperature and wind patterns on several central sites, one of the project teams focused on the concept of an adaptive topography that would vary in Figure 1: Views of parts of site on south side of Tate shape, in response to daily and seasonal variations of Modern Gallery showing proposed landform, parasol environmental parameters, with the aim of providing and activity layers. better conditions for outdoor activity [10]. Proposals for the south side of the Tate Modern Gallery in south London, Fig. 1, evolved following measurements around the site, Fig. 2, and simulations of microclimatic conditions using the Envi-met and Ecotect software, Fig. 3. Parts of the site have good solar access which is a very valuable commodity in a high latitude urban environment of variable sunshine availability. In London wind patterns are both variable and mostly disruptive. As air temperatures are rarely extreme in the city centre, protection from, or exposure to, wind, rain and sun are the deciding factors for outdoor activities. The thrust of the proposals shown in Figs. 1 and 3 is the creation of a dynamic landscape of variable topographic features and surface properties. The team conceived this Figure 2: Positions of measurements of air adaptive topography as consisting of three temperature, relative humidity and wind velocity as complementary layers. The landform layer of recorded by GPS around the Tate Modern site in south London. Figure 3: Landform adaptive strategies for typical April daytime conditions on Tate Modern site, London. Diagrams from left to right: wind (and sunshine) data translated into zones of wind protection and solar access illustrated on landform plan and section; the change in the altitudes of grid points is shown on the hexagonal grid (far right) and site section (bottom). Plea2004 - The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19 - 22 September 2004 Page 3 of 6 stabilised soil sits on an hexagonal grid that regulates 2.3 Urban Shelters upward or downward movement. Sections of points Observations of microclimatic effects around on the grid are moved upward to provide a wind London squares, bus stops and other open spaces, shadow, whilst others may rise to improve solar Fig. 5, led two of the teams to designs for small access, thus dividing the site into areas of wind and pavilion-like shelters [12] [13] for use by passers-by or sun shadow or exposure. Microclimatic simulations bus passengers. These were conceived as being were performed for a range of typical London weather composed of movable elements to provide the conditions to identify the range of movements and adaptive mechanisms, Fig. 6. responses required from the landform layer. Figure 3 illustrates one of these instances. A parasol layer set some 6.0m above the landform is designed to provide selective rain protection or solar control as the case may be, Fig. 1 (top right). Various activity layers can then be inserted into the site combining architectural elements and outdoor furniture with complementary climatic properties, Fig. 1 (top left). Complementary options were explored by a second team with proposals for outdoor elements and furniture for streets and parks, Fig. 4 [11]. Figure 5: Wind patterns around Bedford Square, in central London based on simulations and measurements. Figure 6: Proposals for an “urban living room” to be sited outside the AA School on the pavement of Bedford Square, London. 2.4 Going Underground The stations and passenger areas of the London Underground system provide some striking lessons for students of environmental

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